The number of echoes combined into a single image or image set in multiple echo imaging sequences or echo-train techniques such as rapid acquisition with relaxation enhancement (RARE), fast-spin echo (FSE), and turbo spin-echo (TSE). In RARE imaging, the ETL typically equals the acceleration factor.
As for tooth pain, it is caused by a reaction of the nerves inside a tooth's pulp chamber with the severity dependent upon the type and degree of the stimulus. What follows are some examples of symptoms you may be feeling and their possible causes.
If a tooth is highly sensitive for more than three or four days and reacts to both hot and cold temperatures, itâs best to get an evaluation from your dentist to determine the extent of the problem. Because pain symptoms can be similar, some people might think that a tooth is sensitive when they actually have a cavity or abscess that's not yet visible. Be sure to tell the dentist when the pain started and if there is anything (such as the application of a warm compress) that reduces or eliminates the pain.